Here is a summary from the BMW fluid glovebox printout:
- Brakes (9/1998 and later): "low viscosity" "high performance" DOT 4 (the Bentleys confusingly specify both "low viscosity DOT 4" on page 340-9 and "high performance DOT4" on page 020-11 and just plain old "DOT 4" on page 020-24, while never explaining what "low viscosity" or "high performance" indicates). Some recommend DOT4 ISO6 (aka Class 6, ISO 4925) low-viscosity brake fluid over just regular DOT4, especially in colder climes). While the Bentleys do not specify what viscosity they consider to be "low", further inspection reveals the "BMW QV 34 001" specification seems to support a maximum viscosity @-40°C of 700 mm²/s and a minimum viscosity @100°C of 1.5 mm²/s (both per ISO 3104); most of us agree these specifications can be considered "low viscosity". However many say any DOT 4 brake fluid can be used; and most recommend ATE Super Blue DOT 4 (which does not meet this viscosity specification) or "Original ATE SL.6" brake fluid (which does). Many recommend alternating amber and blue colors to ascertain when the flush is complete; although be advised that the DOT4 specification requires a "clear" fluid, sans die. [Volume: Most people use about 750 ml or about 3/4 quart to flush the four wheels manually and slightly more than a liter to pressure bleed, depending on technique; so buy at least a liter (or quart) to power flush your entire brake system.] Replacement Interval: Every two (2) years (Bentley page 020-9) starting from date of manufacture. Best to use the pressure method, e.g., Motive pressure bleeder; but the two-man push-and-open method still works.
- Brakes (up to 8/1998): "high performance" DOT 4 (nobody seems to know what "high performance" means in practical terms; but the Bentleys clearly specify "high performance DOT4" on page 020-11 and just plain old "DOT 4" on page 020-24 and again on page 340-9). Replacement Interval: Every two (2) years (Bentley page 020-9) starting from date of manufacture.
- Hydraulic clutch (manual transmission only): Uses the same fluid & reservoir as the brake fluid, Bentley 020-26.

- Power steering: Dexron III ATF (realistically, Dexron VI ATF because Dexron III certification is no longer available from GM) Bentley page 020-20. [Volume: It has been said to be just under 2 quarts; I used about a quart to flush twice just my power steering reservoir using a turkey baster to remove fluids out the top.] Note: I6=rack and pinion attached to an aluminum subframe, V8=recirculating ball and nut attached to a steel subframe. Replacement Interval: Bentley says it's "permanently filled"; but most of us would suction out and refill the reservoir with about a quart of fluid every few years because it's a hygroscopic fluid and the permanent filter on the bottom of the reservoir doesn't prevent the fluid from becoming dirty. Some even replace the reservoir in order to have a new filter. Most also replace or cut off the tip of the bottom hoses whose clamp often allows leaks.

- Engine oil (E39 1999 & later): 15W40 LL-01 mineral oil BMW PN: 07.51.0.017.868 (amazingly, only one SAE weight is specified! Don't be confused because Bentley page 020-11 lists only SAE 15W40 while page 020-9 confusingly lists only SAE 5W30 & SAE 15W40 but page 020-11 appears to be the specific listing to follow). Various dogmatic camps differ on 'opinions' (1) but there is only one BMW-approved list (1). [Volume: I6=6.9 quarts, V8=7.9 quarts]. Replacement Interval: The instrument cluster Service Interval Indicator (SII) will determine when necessary by lighting the yellow light and indicating "OIL SERVICE". On average, most seem to change oil & filter (Mann, Hengst, or Mahle only!) & 36mm 6-point socket oil-filter cap o-ring (91x4mm) & copper crush washer roughly thrice a year at about 4,500 miles; most replace the smaller lower oil-filter-post o-rings every five years or so (7x2.5mm). Keep a spare 17 mm drain bolt handy on the I6 as it's hollow and can break from over tightening (M12x1.5x18mm). Torque filter cap to 18 ft-lb, drain bolt to 21 ft-lb. Note: Mixing oil types (mineral vs synthetic) is permissible; but bear in mind "synthetic" is an advertising term and quite a few oils labeled as such are not PAOs or diesters (1). Best to use either the oil-pan gravity-drain method or the MityVac vacuum-extraction method (don't use the Motive vacuum extractor). Most replace the oil filter & oil-filter-cap o-ring on every oil change and the lower small o-rings on every other change. Keep a spare oil drain plug handy, especially in the I6 as the bolt is hollow and prone to breaking when over torqued.
- Engine oil (gas, E39 1997 & 1998): Synthetic 5W-30 LL-01 (aka long-life 2001) BMW PN: 07.51.0.017.866 (amazingly, only one SAE weight is specified! This is confusing because Bentley page 020-11 lists only SAE 5W30 while page 020-9 confusingly lists only SAE 5W30 & SAE 15W40 but the 020-11 appears to be the specific listing). Replacement Interval: The instrument cluster Service Interval Indicator (SII) will determine when necessary. Note: Mixing oil types (mineral vs synthetic) is permissible. On average, most seem to change oil & filter roughly thrice a year at about 4,500 miles.
- Engine oil (diesel): I can't find anything in the Bentleys; but the euro owners manual lists on page 152 "ACEA: A3/B3 or ACEA: A3/B4" specifications which all long-life-01 oils meet (according to that owners manual). Most people here say to use LL-04 approved oils (1). Replacement Interval: The instrument cluster Service Interval Indicator (SII) will determine when necessary.

- Air conditioner: Refrigerant 134a (aka R-134a) with poly alkylene glycol oil, sometimes referred to as poly alkaline glycol oil (aka PAG refrigerant oil). Bentley book II, 640-2 & 640-3 & 640-23. The PAG oil is known by other names such as ND8, PAG46, and BMW PN: 82.11.1.468.042 and travels with the refrigerant as a mist. Best to empty and then refill refrigerant by total weight; second best is the evaporator temperature method (i.e., in the shade, ambient temperature less than about 75°F and relative humidity below about 60% - then add R-134a until the evaporator exit air temperature with A/C set on max at 60°F is 4°C/39°F or colder - the best you can do without MoDIS is probably the center-dash vent at something like 10°C/50°F); third best is the pressure method (i.e., add refrigerant until the low-pressure side is 25 psi to 45 psi ... aim for around 32 psi (assuming shade, ambient, & humidity listed prior); worst is by can weight (e.g., adding a 12oz by weight can or a 16oz can by weight but the AC is a critical-charge system that won't tolerate refrigerant quantities much outside + or - .05 kg). [Volume: E39's built up to 12/97 contain 1,225 grams +/- 25 grams (2.70 lbs +/- 0.05 lbs) of R-134a; E39s built after 12/97 contain 750 grams +/- 10 grams (1.65 lb +/- 0.03lb) of R-134a. The amount of PAG oil misted in the system is said to be about 1 ounce by volume.] Replacement Interval: Lifetime charge.

- Differential (conventional, i.e., non-limited-slip E39s): The Bentleys specify "BMW SAF-XO synthetic final drive gear oil" which doesn't exist (it's Castrol). The Bentleys don't specify the weight (it's SAE 75W-90); and the Bentleys don't specify the quality (it's API GL-5 hypoid gear oil). Given that, suitable replacements are Amsoil Synthetic Manual Transmission Fluid (MTF) API 75W90,Mobil1, Royal Purple Max-Gear, & Redline SAE 75W90 API GL-5 synthetic gear oils. Unfortunately, there's no way to tell which of the three (3) different differentials you have w/o looking at the numbers molded into the metal. Bentley page 020-11 & 020-26 & 331-6. [Volume: Type G=1.7 quarts, Type 188 Compact=1.1 quarts, Type 220/215 Compact=1.5 quarts.] Replacement Interval: Lifetime fluid (but most recommend replacing differential fluid at the same time you replace transmission fluid, which is about 5 years or roughly 60K miles).
- Differential (limited-slip E39s, such as the M5): BMW SAF-XJ API GL-5 SAE 75W-140 synthetic hypoid final-drive gear oil (aka Castrol SAF-XJ). This requirement is not listed in the Bentley manual; it is gleaned from the Castrol literature and from what is stated about the M5 in this thread below (please correct if necessary). Replacement Interval: Lifetime fluid (but most recommend replacing differential fluid at the same time you replace transmission fluid, which is about 5 years or roughly 60K miles).

- Battery: A charged battery is 33.5% (volume/volume%) sulfuric acid (4.2 Molar H2SO4, ) & distilled water (Bentley 020-23) with positive plates containing lead dioxide (PbO2) and negative plates of lead (Pb), both mixed with calcium (Ca) to minimize gassing (i.e., loss of water) and other elements (such as tin, antimony, & selenium to harden the plates and simplify manufacturing) in a polypropylene case. In the discharged state, both plates turn to lead sulfate (PbSO4) as the electrolyte loses its dissolved sulfuric acid and becomes primarily water (which can freeze in cold temperatures and the lead sulfate may form insoluble crystals which, over time, reduce the capacity of the battery if it is not recharged immediately after discharge). [Total Volume: unknown but users have reported adding about 20 ml per cell after two years of use]. Replacement Interval: Lifetime fluid (top off only if needed, after removing steel strap, two stickers and then unscrewing the six cell caps, and filling to the fill line which is 1/4 inch or 5mm above the top of the plates at the very bottom of the internal black plastic depth indicator). The OEM battery has built-in hydrometer where green indicates a charged battery and black indicates a discharged battery, and yellow indicates a defective battery. Better to test at 27°C/80°F by loading battery with 15 amperes for 1 minute (or just turn headlights on w/o engine running) and then perform a 1.265 specific-gravity hydrometer test of each of the six cells (add or subtract 0.004 to the hydrometer reading for every 10°F/6°C above or below 27°C/80°F respectively); and a 12.6 volt open-circuit voltage test across the battery terminals (Bentley 121-5, 121-6). OEM specs are BMW 61.21.8.381.762, USA 729905-10, EN 12V 90Ah 720A, SAE 160 RC 720 CCA. Aftermarket batteries are Duralast 49-DL, Duralast 94-R, NAPA #7549, Deka 649MF, Interstate MTP-93; must have side vent and a stamped date code within the last couple of months.

- Engine fuel (gas): The sticker on the inside of the fuel filler specifies the octane rating to use; most E39s in the USA specify unleaded 91 AKI (the AKI is the average of the RON & the MON). Lower octane ratings can be used as the two piezoelectric knock sensors will retard timing if they sense detonation vibrations which may adversely affect performance but which won't damage the car under normal circumstances. [Volume: 70 liters (18.5 gallons) with a reserve capacity of 8 liters (2 gallons) in the 525i & 530i and a reserve of 10 liters (2.5 gallons) for the 540i]. We're not sure the algorithm for the small round yellow fuel-warning light, but most people say it goes on approximately at 40 miles remaining fuel; chime sounds at approximately half that (need more data). Replacement Interval: Monthly, as fuel reputedly goes "stale" after 30 days; also it's reputed you should fill by the 1/4 to 1/8 mark in order to better cool the fuel pump. Fuel can't be siphoned out due to siphon restrictions 4 inches in but can be bled using other methods.
- Engine fuel (diesel): On page 23 of the Owners Manual, it lists "Diesel oil DIN EN 590", whatever that is. It specifically says not to use rapeseed oil methyl ester (aka RME), or bio diesel oil. Replacement Interval: As needed?

NOTE:
Our decision-making algorithms fit into a small number of categories, vastly influenced by marketing (i.e., influenced by "the big lie"). I've taken college inorganic and organic chemistry (like most of us have) and have made my own decisions about what fluids to use (like all of us have). While I'm in the "gas is gas", "oil is oil", "antifreeze is antifreeze" dogmatic camp, I did realize when writing this that others don't think similarly ... so please continue to improve this listing so that it forms a generally accepted view of the tribal 'we'.